Synopsis

Description

dblink_build_sql_update can be
useful in doing selective replication of a local table to a
remote database. It selects a row from the local table based on
primary key, and then builds a SQL UPDATE command that will duplicate that row, but
with the primary key values replaced by the values in the last
argument. (To make an exact copy of the row, just specify the
same values for the last two arguments.) The UPDATE command always assigns all fields of the
row — the main difference between this and dblink_build_sql_insert is that it's assumed
that the target row already exists in the remote table.

Arguments

relname

Name of a local relation, for example foo or myschema.mytab. Include double quotes if the
name is mixed-case or contains special characters, for
example "FooBar"; without quotes,
the string will be folded to lower case.

Values of the primary key fields to be used to look up
the local tuple. Each field is represented in text form. An
error is thrown if there is no local row with these primary
key values.

tgt_pk_att_vals_array

Values of the primary key fields to be placed in the
resulting UPDATE command. Each
field is represented in text form.

Return Value

Returns the requested SQL statement as text.

Notes

As of PostgreSQL 9.0, the
attribute numbers in primary_key_attnums are interpreted as logical
column numbers, corresponding to the column's position in
SELECT * FROM relname. Previous versions
interpreted the numbers as physical column positions. There is a
difference if any column(s) to the left of the indicated column
have been dropped during the lifetime of the table.